1. Field of the Invention
The field of the present invention relates generally to gate operators that raise and lower gates to allow passage through a gate opening. More particularly, the present invention relates to gate operators that vertically raise and lower a gate about a horizontal axis wherein the gate raises and lowers in a generally 90 degree arc by the power of a fractional horsepower motor. Even more particularly, the present invention relates to gate operators that utilize the weight of the gate during the gate lowering process to store energy in an energy accumulator mechanism for use in raising the gate.
2. Background
Gate operators are commonly used to open and close security gates or other barriers, such as crossing arms, to control ingress and egress from residential, business, industrial, recreational and ranch properties. Gate operators open and close gates in a variety of different manners. Many gate operators open and close the gate by moving it in a horizontal or linear direction or by swinging the gate across the gate opening by pivoting the gate around a vertical axis. These gate operator systems require sufficient space around the gate and gate mounting structure to allow the gate to move between the open and closed positions. Because the gate must move across the surface of the ground, the build-up of various materials around the gate structure, such as snow, sand and dirt, can cause problems for operation of the gate if the build-up prevents free movement of the gate.
To avoid the problems associated with gate operators that open the gate in a horizontal or linear direction or around a vertical axis, some gates open vertically by pivoting around a generally horizontal axis. Typically, these gates are mounted on the gate structure to allow the gate to pivot between the open and closed positions such that the gate pivots up to open and down to close. One benefit of this type of gate operator is that movement of the gate is not impeded by snow, sand, dirt or the like in the roadway leading to or from the gate or around the gate structure. An additional benefit of this type of gate operator is that use of the gate is not limited by the sloping topography of the roadway across which the gate extends. Further benefits of this type of gate operator is that it reduces the amount of space required for the gate along the roadway and gate structure and has minimal site preparation requirements. Because these type of gate operators move the gate within its own space, there is reduced impact on the associated landscaping.
Often security gates are utilized in remote areas that are not served or not reliably served by electrical power. Consequently, many security gates rely on battery or other remotely available power supplies to supply electrical power to an electric motor. To ensure that power is available to the gate operator when needed, it is important for the gate operator motor to have relatively low power consumption.
An example of a vertically opening gate operator is found in U.S. Pat. No. 4,779,379 to Steen. This patent describes a gate operator for raising or lowering a gate about a horizontal axis located near the lower proximate corner of the gate. The gate operator lifts the gate in a 90 degree arc in the plane of the gate using a large belt-driven pulley, a vertical raceway on the face of the driving wheel and a linkage mechanism. This gate operator is configured to counterbalance the weight of the gate through use of a number of springs that serve to make the gate effectively weightless in all positions of its arcuate movement, such that the gate operator requires a minimum amount of force, and as a result electrical power, to move the gate between the open and closed positions.
Although the vertical movement gate operator described above avoids some of the problems associated with gate operators that move the gate in a horizontal or linear direction or swing the gate about a vertical axis, it has a number of problems that have prevented it from being widely utilized. These problems include an opening and closing mechanism that is relatively difficult to install, typically requiring more than one site visit, and operate, such that it has a tendency to be somewhat troublesome during operation. In addition, this gate operator is difficult to regulate and adjust for a given gate length, weight and design. The gate operator described in U.S. Pat. No. 4,779,379 is complicated to adjust, having three adjustment points, various lever fulcrums and chain variations. Consequently, a need exists for a gate operator that has the benefits of a vertical movement gate operator, including relatively compact gate size and low power consumption, that is simple to install and operate and less subject to problems.